By Miyoung Kim SEOUL (Reuters) – Samsung Electronics Co Ltd is bracing for its weakest smartphone profit growth this year since 2007 as arch rival Apple Inc challenges its domination in China's $80 billion market. Samsung's mobile devices business, which earns two thirds of the company's profit, will come under pressure when Apple makes its phones available from January 17 via China Mobile Ltd, through which Samsung has been selling smartphones for around seven years. Apple is also widely expected to sell smartphones with larger screens come autumn when it traditionally announces products, neutralizing a selling point that Samsung has enjoyed since introducing its Galaxy Note in late 2011.